Adsorption of Sunscreen Compounds from Wastewater Using Commercial Activated Carbon: Detailed Kinetic and Thermodynamic Analyses

Sunscreen compounds are one of the most toxic substances detected in the aqueous environment. However, these molecules are continuously utilized in a various range of products to provide protection against UV radiation. The removal of three sunscreen compounds, 4-hydroxybenzophenone (4-HBP), 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3), by commercial activated carbon (AC) was investigated using batch adsorption experiments. Different operational characteristics, such as adsorbent dosing, interaction time, solution pH and starting sunscreen compound concentration, were studied. The adsorption capacity of the AC material was assessed using a liquid chromatograph associated with a mass spectrometer detector (LC–MS/MS). Two isotherm models were utilized to explained the target compound adsorption phenomenon (Langmuir and Freundlich), while pseudo-first and -second kinetic orders and thermodynamics were utilized to examine the adsorption mechanism. The maximum adsorption capacities determined from the Langmuir isotherms were established as 43.8 mg/g for 4-HBP, 48.8 mg/g for BP-3 and 41.1 mg/g for BP-1. The thermodynamic parameters revealed the following: a negative ΔG° (